The invention relates in general to a communication network of the type in which various user sets, denoted peripheral apparatuses hereinafter, such as, for example, work stations, printers etc. can optionally be connected in geographically different locations to this communication network. To that end use is made of universal modular coupling units which act as an interface between a relevant peripheral apparatus and the communication network, it then being possible for such a peripheral apparatus to be detachably connected to this communication network. Thus, users can connect, according to their requirements and in optional positions, a relevant peripheral apparatus to the communication network. This implies that the geographical location addresses, denoted physical addresses hereinafter of the peripheral apparatus connected to the communication network can be different considered in the time. Generally, each peripheral apparatus having access to the communication network is uniquely characterized by what is commonly referred to as a functional address. Thereby the functional identity such as type and characteristic of each peripheral apparatus is fully and unambigously determined. Thus, each peripheral apparatus connected to the communication network can be addressed and checked, for example in connection with control functions to be remotely performed. For performing a diagnostic function it is, however, required at all times to have the availability of the physical addresses of the peripheral apparatus connected to the communication network. To that end, an address portion which might serve as a variable physical address for the relevant peripheral apparatus might be added to each functional address. However, such an approach does not ensure a simple and reliable diagnostic.
The invention has for its object to improve a communication network of the above-defined type such that on the one hand the physical addresses of the relevant peripheral apparatuses can be changed in a simple way without user-unfriendly disciplines, on the other hand that a diagnostic system module can be informed in an unambiguous and reliable way of these physical address data which are required in addition to the functional address data for a complete performance of the diagnostic system functions.
Within the framework of the invention there is however the problem that the reporting of the physical address data from such coupling units must satisfy a number of different requirements. The most important of these requirements are: the physical address information must be generated within a comparatively small physical volume, the address generating procedure must be initiated autonomously on connection of the peripheral apparatus to a coupling unit, an adequate number of different address codes must be available, it being a prerequisite that a desired address code is adjustable in a simple way on installation, the generating procedure must be immune within predetermined limits from supply voltage fluctuations, the address reporting must be accompanied by a low power consumption, and the cost price must be economically attractive.
Taking the above-described problems as a starting point, the invention is further based on the recognition that the modular coupling units are connected permanently and at a fixed location to the communication network and thus may be sources for the various physical addresses necessary in connection with the diagnostic function.